The ever-decreasing size of microelectronic devices and the rapid development of microelectromechanical systems (MEMS) have created a great need for high energy density micropower supplies, for example, a power supply for microelectronic devices. Typically, conventional battery technology is used in these applications. However, current battery technology has a very low energy density, on the order of from 0.035 to 0.350 kWe-hr/kg. An alternative to batteries is to combine a small fuel cell with a micro-hydrocarbon fuel processor. In this case, the size of a fuel processor's primary converter, e.g., fuel reformer, must be reduced. It is also desirable to lower the operating temperature of fuel reformer. This is difficult because the combustion and, therefore, the reforming processes are no longer stable. The lower operating temperature favors the more desirable products (hydrogen and carbon dioxide) in the reforming reactions and also makes thermal management and integration easier, especially on this small size scale. However, providing stable heat for the endothermic reforming processes is difficult, due to the fact that stable combustion is generally self-sustaining only at temperatures in excess of 1000° C. The instability of the combustor operation leads to partial vaporization of the hydrocarbon fuel, if it is liquid, and to less than desired conversion of the hydrocarbons to a hydrogen rich product stream due to the intermittent lack of energy for the endothermic reactions. On the other hand, combustion expedited by catalysts, catalytic combustion, can be stable down to lower temperatures of about 200° C.
There remains a need for microcombustors and fuel reformers which have a very small size, steady performance, and operate at low temperature while maintaining high efficiency levels.